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Jan 20, 2015

Building a simple LAMP Application using Docker

As part of our team's effort to familiarize ourselves with Docker we wanted to start with a simple and well understood use case. To do so, we decided to build a small LAMP application on Fedora 21 Server (not F21 Workstation and not F21 Cloud). This helped us get to grips with the platform and in the event that it might help others, I thought it was worth sharing. Thanks to Erin Boyd, Jeff Vance, Scott Creeley and Brad Childs for their help in putting this together.

The application can be built in 4 relatively simple steps:

1) Set up your Docker Host environment

2) Launch a PHP Container

3) Launch a MySQL Container and create a Database

4) Write a simple PHP app that queries the database.

1. Setting up your environment

This tutorial offers a straightforward guide to setting up Fedora 21(F21) as your Docker Host.

2. Configuring and launching the PHP Container

In order to serve the PHP page, we'll need a docker image that provides a PHP enabled Web Server. We can get this image from the docker hub by simply typing "docker pull php". You can then type "docker images" and you should now see the php image in your list of local images.

One of the first things you need to understand about Docker is the relationship between containers and your data. The best practice is to store the data outside of your container and then mount the external store onto a directory within the container. This model allows you to have the PHP runtime inside a container but the actual PHP pages being served from an external location, such as a directory on the Host (F21) filesystem.

To do this, you must select an EXISTING directory on F21 to host the PHP pages. In our case, we selected /opt/php/. Then you can simply launch a PHP container from the image and mount /opt/php onto /var/www/html using the -v parameter as follows:

The next step is to create a simple php files in /opt/php and verify that the page is being served by the container. When you launched the container, Docker will return a ContainerID. In order to obtain the IP address of your PHP container, run:

docker inspect [ContainerID] | grep "IPAddress"

Next, launch a browser in F21 and use the IP of the PHP container in the URL, for example - http://172.17.0.17/helloworld.php

You should now be serving webpages! However, there's one more wrinkle. Unfortunately, the PHP image we're using does not contain any MySQL client libraries. To resolve this, we'll create a layered image that extends the PHP image that includes the MySQL client libraries.

1. Stop the old container:

docker stop [ContainerID]

2. Create a new directory, such as /opt/mynewphpimage

3. Create a new file in the directory called "Dockerfile" and add the contents below:

FROM php:5.6-apache

RUN docker-php-ext-install mysqli

4. Generate the image called "php-mysql" using the following command:

docker build -t php-mysql .

Finally, launch a new container with your new image that is mounted to the :

Now that we have our PHP container all set up. The next step is to setup the MySQL container which means we'll need a MySQL Docker image. I used the tutum/mysql image and you can install it by running "docker pull tutum/mysql". You can then run "docker images" on your F21 Host and you should now see the tutum/mysql image in your list of local images.

MySQL will be set up the same way as the PHP Container was in that the actual database files will be persisted to /opt/mysql on the Fedora 21 Host and the container will only contain the MySQL runtime. This blog post describes how to do that, as well as create a small database using the container. You can verify the database files are in /opt/mysql after it has been created.

Lastly, you'll need to ensure that you create a user in MySQL that has access to the appropriate tables and database that you created, so that the PHP MySQLi client can use it to connect to them. I did this using the mysql command within the MySQL container as demonstrated below: